I do too. And, like you, I don't know if it will ever be shown. Not in this show anyway.

 

I figure any Autobot or Cybertronian in proximity of the Matrix is capable of being the next Prime--Optimus said that it isn't for him to choose the next Prime, but the Matrix's. He said that it would present itself before anyone worth of it.

Alpha Trion pointed out that even someone as inexperienced as Orion Pax could be molded into a Prime via the Matrix, so in instances where no one pure of spark is present, the Matrix would probably bound with someone was as unruly as Wheeljack or someone as deceitful as Starscream even, transforming its host into the leader he/she needs to be.

Imagine if Megatron actually killed Optimus and claimed the Matrix for himself, only to have it consume him, transforming him into the next Prime and leader of the Autobots:eek

 

Well it presents itself to one that is worthy, not just anybody. Alpha Trion tells Optimus he can die since Smokescreen is near and a worthy candidate. You're given access to the wisdom of the Primes, but having access doesn't mean somebody will put it to good use. Starscream would still be Starscream and Megatron would still be Megatron- they'd just be smarter. Eek.

If it transformers any old person into a leader they could've just grabbed somebody off the street and stuffed the Matrix* in them instead of waiting so long for a "worthy candidate" to show up. They could've just given Megatron* the Matrix and prevented the war.

Edit: *as in, chucked them in front of Primus.

 

Apart from Smokescreen's line upon seeing Darkmount fall, i'm tempted to say Optimus is really Smokescreen's spark in a new body with Optimus inhabiting Screen's.